Transistorized ignition system with a saturable transformer control and voltage compensation means



March 12, 1968 0. K. NILSSEN 3,373,314

TRANSISTORIZBD IGNITION SYSTEM WITH A SATURABLE TRANSFORMER CONTROL ANDVOLTAGE COMPENSATION MEANS Filed June 25, 1965 r 2 Sheets-Sheet 1 @f I33 65 6'59 2s 57 56 92 EL 58 {:27 7s IQ44 2 OLE K. NILSSEN INVENTORMKSIZM March 1 2, 1968 3,373,314

TRANSISTORIZED IGNITION SYSTEM wnn A SATURABLE TRANSFORMER O. K. NILSSENCONTROL AND VOLTAGE COMPENSATION MEANS 2 Sheets-Sheet 2 Filed June 25,1965 OLE K. NILSSEN INVENTOR ATTORNEYS United States Patent 3,373,314TRANSISTGRIZED IGNITIGN SYSTEM. WITH A SATURABLE TRANSFGRMER CUNTRQL ANDVOLTAGE CONEFJNSATIGN MEANS Ole K. Nilssen, Livonia, Mich, assignor toThe Ford Motor Company, Dearborn, Mich, a corporation of Delaware Filed.lune 25, 1965, Ser. No. 466,949 Claims. ((31. 315-214) ABSTRACT OF THEDISCLGSURE An ignition system for an internal combustion engine in whichmeans are employed for charging an electrical storage means from asource of electrical energy to a substantially constant valueirrespective of fluctuations in the terminal voltage of the source ofelectrical energy. This electrical storage means is charged immediatelyprior to the requirement for ignition voltages from the electricalstorage means. The means for charging the electrical storage meanscomprises a transistor or other solid state switching device, asaturable switching transformer or core and circuit means coupling thetransistor and the saturable switching core or transformer for causingthe transistor or other solid state switching device to be switched tothe conducting state only during the time that the saturable switchingtransformer or core is switched from a steady state operating conditionto one of its states of saturation. Circuit means are coupled to thesource of electrical energy and the saturable switching transformer orcore for biasing the saturable switching transformer or core toward onestate of saturation as a function of the terminal voltage of the sourceof electrical energy and this means may comprise a winding coupling thesaturable switching transformer or core and connected across the sourceof electrical energy.

This invention relates to an ignition system for an internal combustionengine, and more particularly to an ignition system for an internalcombustion engine in which the output or ignition power is maintainedsubstantially constant notwithstanding wide variations in the terminalvoltage of the source of electrical energy that supplies the system.

The present invention is particularly applicable to solid state ortransistorized ignition systems, and may be employed with the ignitionsystem shown and described in my copending application S.N. 403,263,filed Oct. 12, 1964. In that system, a transistorized ignition system isshown in which a saturable switching core is used to control atransistor or other solid state switch that is coupled to the source ofelectrical energy or storage battery and the primary winding of anignition coil. In that system, the transistor or solid state switch isbiased to its con ducting state when the core switches from a steadystate operating point into a condition of saturation. As a result, theprimary winding of the ignition coil is energized during this period andthis period is substantally constant for any given battery voltage andis independent of engine speed.

The present invention provides automatic compensation for changes in thecoil energy level that would accompany changes in the terminal voltageof the battery in the above described system. This is done by applying abias to the saturable switching core that biases at least a portion ofthe core toward that state of saturation wh ch terminates the conductingtime of the transistor. The value of this bias is substantiallyproportional to the terminal voltage of the source of electrical energyor battery. As a result, the on time of the transistor or the solidstate switching device that energizes the primary winding of the3,373,314 Patented Mar. 12, 1968 "ice ignition coil is substantiallyinversely proportional to the terminal voltage of the battery. It isaxiomatic that the amount of electrical energy that can be stored in theprimary winding of an ignition coil in a given time period variessubstantially proportionally to the terminal voltage of the source ofelectrical energy that is coupled directly thereto. The system describedprovides, therefore, an automatic compensation in which the electricalenergy level to which the primary winding of an ignition coil is chargedduring each ignition cycle is substantially constant regardless of andindependent of wide variations in the terminal voltage of its source ofelectrical energy.

The output power of the ignition system, therefore, that is produced inthe secondary winding of the ignition coil remains substantiallyconstant notwithstanding variations in the terminal voltage of thesource of electrical energy that may occur during normal operations ofthe automotive vehicle. These variations may be particularly extremeduring the starting of the internal combustion engine. The output powerof the ignition system is also independent of engine speed.

Although the invention has been described above in relation toconventional electrical storage devices used in automotive vehicles, forexample, an ignition coil having a primary and a secondary winding inwhich the electrical energy is stored in inductive form in the primarywinding of the ignition coil prior to the requirement for ignitionvoltages, it may also be used with a capacitive discharge system inwhich the electrical energy is stored in a capacitor just prior to thetime that ignition voltages are required by the spark plugs of theengine.

An object of the invention is the provision of an ignition system inwhich the output power remains substantially constant notwithstandingwide variations in the terminal voltage of the source of electricalenergy or storage battery that supplies electrical energy to the system.

A further object of the invention is the provision of an ignition systemfor an internal combustion engine in which the time that an electricalstorage device in the system is energized from a source of electricalenergy is substantially inversely proportional to the terminal voltageof the source of electrical energy.

A further object of the invention is the provision of an ignition systemfor an internal combustion engine in which an electrical storage devicein the system is charged to a substantially constant level of electricalenergy just prior to the time for the requirement for ignition voltagesdespite wide fluctuations or variations in the terminal voltage of thesource of electrical energy for the system.

A further object of the invention is the provision of an ignition systemfor an internal combustion engine that will supply a constant amount ofelectrical energy to the ignition means or spark plugs of the engineirrespective of and independent of engine speed and the terminal voltageof the source of electrical energy supplying energy to the system.

Other objects and attendant advantages of the present invention may bemore readily realized when the specifica tion is considered inconnection with the attached drawings in which:

FIGURE 1 is a circuit diagram of one embodiment of the invention;

FIGURE 2 is an enlarged partial circuit diagram of the saturableswitching core or transformer used in the circuit of FIGURE 1;

FIGURE 3 shows the resultant hysteresis loops of the saturable switchingtransformer or core shown in FIG- URE 2 as the result of varying amountsof bias applied to the core;

FIGURE 4 is a circuit diagram of another embodiment of the invention,and

FIGURE 5 is a hysteresis loop of the saturable switching core ortransformer used with FIGURE 4.

Referring now to the drawings in which like reference numerals designatelike parts throughout the several views thereof, there is shown inFIGURE 1 a schematic electrical diagram of one embodiment of theinvention in which an ignition coil has a primary winding 11 and asecondary winding 12. The secondary winding 12 is connected through lead13 to rotating arm 14 of a distributor 16. This rotating armsequentially connects a plurality of spark plugs 17 to the secondarywinding 12 of ignition coil 10 through the lead 13 and the leads 18,19,20, 21, 22 and 23.

The primary winding 11 of ignition coil 16 is connected to the negativeterminal 26 of a sourre of electrical energy or storage battery 27through leads 28 and 31. The other terminal of the primary winding 11 oftheignition coil 10 is connected through lead 32 to the dot markedterminal of a winding 33. The other terminal of the winding 33 isconnected through lead 34 to an output electrode 35 of a solid stateswitching device 36. The solid state switching device 36 preferablytakes the form of a transistor and theoutput electrode 35 takes the formof the collector of this transistor. The other input electrode 37 of thesolid state switching device 36, which in transistor form is theemitter, is connected through leads 41, 42 and 43 to the positiveterminal 44 of the source of electrical energy 27.

A saturable switching core of transformer 51 is employed to control theconduction of the solid state switching device or transistor 36. Thissaturable switching core or transformer has a first winding 52 havingits dot marked terminal connected to the positive terminal 44 of thesource of electrical energy or battery 27 through lead 53, resistor 54,lead 55, lead 42 and lead 43. The other end or terminal of the winding52 is connected through lead 56 with contact 57 of ignition contactbreaker points 58. The other contact 59 is connected to the lead 31 andhence to the positive terminal 26 of the source of electrical energy 27through movable arm 61 and lead 62.

The ignition contact breaker points 58 are normally biased to a closedposition and are separated or opened periodically by a cam 64 thatoperates a follower 65 coupled to the arm .61. This cam is operated insynchronism with the rotatable arm 14 of the distributor 16, as shown bythe dotted lines 66, and it is arranged so that the ignition contactbreaker points 58 open just shortly before the rotating arm 14 makescontact with the leads 18 through 23 respectively of the distributor 16.

The saturable switching core or transformer 51 also has a secondwinding, previously described, in the form of winding 33 wound thereonso that its dot marked terminal is connected to the primary winding 11of the ignition coil 10 through the lead 32 and the unmarked terminal isconnected through lead 34 with the collector 35 of the solidrstateswitching device or transistor 36.

A third winding 75 in the form of a feedback winding has its dot markedterminal connected through a lead 76 to a control electrode or base 77of the solid state switching device or transistor 36 while the other endof the winding 75 is connected through lead 73, resistor 81 and lead 82to the lead 42. The lead 42, as previously stated, is coupled to theoutput electrode 37 ,or emitter of the solid .state switching device ortransistor 36 through the lead 41 and is also connected to the positiveterminal 44 of the electrical storage battery 27 through the lead 43.

A cross bar 91 of conductive magnetic material is provided with one endpositioned intermediate the windings 33 and 75 and the other endintermediate the windings 33 and 52. A winding 92 is positioned on themagnetic cross bar 91 and it has one end connected through lead 93,resistor 94, lead 95, lead 42 and lead 43 to the positiveterminal 44 ofthe source of electrical energy 27. The other end of the winding 92 isconnected to the negative terminal 26 of the source of electrical energy27 4 through leads 96, 62, 31 and 28. As a result of the connection ofthe winding 91 to the source of electrical energy 27 by the circuitmeans described above, a magnetic him is permanently applied to thesaturable switching core or transformer 51 during the operation of theignition system.

The operation of the circuit will now be described, assuming that asmall amount of bias is applied by the winding 92 as will be the casewhen the terminal voltage of the source of electrical energy or battery27 is low.

The effect of varying terminal voltages that vary the' amount of currentthrough the winding 92 will be explained subsequently.

With the contacts 57 and 59 of the ignition contact breaker points 58closed, a circuit will be established through the first winding 52 onthe saturable switching core 51 from the source of electrical energy orbattery 27. The resistance of this circuit, including the resistance ofresistor 54 and the resistance of the winding 52, is such that thenumber of ampere turns or volt seconds applied to the core 51 issufiicient to bias it into a negativestate of saturation as designatedby the letter A in FIGURE 3. At this time, the solid state switchingdevice or transistor 36 will be in a nonconducting state because novoltage will be developed at this time across the feedback winding 75,and the emitter 35 and the base 77 will be at the same potential. Sincethe solid state switching device 36 is in the nonconducting state, therewill be no current through the primary winding 11 of the ignition coil10 nor through the winding 33 of the saturable switching core 51.

It should be noted that with the dot convention employed here, currentinto a dot marked terminal will produce a magnetizing force to drive thecore toward a nega-,

tive state of saturation (point A) while current into an unmarkedterminal will produce a magnetizing force to drive the core toward apositive state of saturation (point C). Similarly, a flux change from anegative flux state toward a positive flux state will produce a negativevoltage at a dot marked terminal of a winding with respect to itsunmarked terminal and a flux change from a positive flux state toward anegative flux state will produce a positive voltage at a dot markedterminal of a winding with respect to its unmarked terminal.

When the ignition contact breaker points 58 open under the action of thecam 64 and follower 65, the bias on the saturable switching core will beremoved and the flux level will fall to the remnant fiIlX level at B.This changing flux will induce in the feedback winding 75 a negativepotential at the dot with respect to the potential at the other end ofthe winding 75. This will turn the transistor to a conducting state, andprovide current flow through the primary winding 11 of the ignition coil10 and through the winding 33 connected in series with the primarywinding 11. Since current flows into the unmarked terminal of winding33, the core will be switched toward a positive state of saturation anda negative potential will be produced at the dot marked terminal withrespect to the unmarked terminal of feedback winding 75, thereby turningthe transistor to its fully conducting state by virtue of this feedbackaction. Current through winding 33provides suflicient magnetizing forceon the saturable switching core 51 to drive it from point B into asaturated condition at point C.

When the saturable switching core reaches the saturated state at pointC, the feedback voltage in the winding 75 will fall to zero therebyturning off the transistor or solid state switching device 36 andinterrupting the current flow through the primary winding 11' ofignition coil 10. This interruption of the current flow will induce avoltage in the primary winding 11 and a stepped up ignition voltage inthe secondary winding 12 which will be applied at this time to one ofthe spark plugs through the lead 13, the rotatable arm 14, and one ofthe leads 18 through 23 of the distributor 16. This voltage will alsoact on the winding 33 and tends to reset the core backtow'ard the pointA since the voltage across the primary winding 11 has reversed so that apositive potential appears at the dot marked terminal of the winding 33.A positive potential will also be present at the dot marked terminal offeedback winding 75 thereby keeping the solid state switch ing device oftransistor 36 in the cutofi condition.

A diode 97 positioned in the lead 34 prevents the saturable switchingcore 51 from being fully reset by the ignition voltage as it appearsacross the primary winding A1 of the ignition coil 10 since it preventscurrent flow into the dot marked terminal of the winding 33 that wouldhave the eliect of resetting the core back to point A in FIGURE 3. Thus,rather than being moved down to the point A in FIGURE 3, which is anunstable position when the ignition contact breaker points 47 are open,the magnetization of the core will now fall only to point D which is astable position of residual flux. As soon as the contacts 57 and 59 ofthe ignition contact breaker points '8 close, the magnetization of thecore will be switched back to point A and another ignition cycle willoccur only when the contacts 57 and 59 of the ignition contact breakerpoints 58 open.

It can be appreciated from an inspection of the circuit diagram ofFIGURE 1 that the magnitude of the current through the winding 92 woundon the magnetic cross bar 91 is directly proportional to the terminalvoltage of the source of electrical energy 27. It can be appreciatedalso that the time the primary winding 11 is energized is the timeduring which the solid state switching device or transistor 36 is in aconducting state. This time is in turn controlled by the period in whicha voltage is induced in the feedback winding 75 connected between thebase 77 and the emitter 37 of the solid state switching device ortransistor 36. This voltage is in turn induced in the feedback winding75 only during the time in which a change of flux linking the winding 75and contained in the core 51 is maintained.

An examination of FIGURE 2 will disclose that in the portion of the corelinked by the first winding 52. that drives the core toward thesaturated state A, that the flux produced by the winding 91 in thatportion or" the core aids the flux produced by the winding 52 when thatwinding is energized by the closing of the ignition contact breakerpoints 57 and 58. It is apparent also that current through the winding33 when the solid state switching device or transistor 36 is in aconducting state produces a flux that aids the flux produced by thewinding 91 on that portion of the core on which the winding 33 is wound.

The larger the current, therefore, through the winding 91, the largerwill be the flux that aids the flux produced by the winding 52 in thatportion of the core and also the larger will be the flux which aids theflux in the winding 33 in the portion of the core on which that windingis wound. The net effect of this is to shrink the hysteresis loop, asshown in FIGURE 4, as current through the winding 91 increases, since aflux change that links the feedback winding 7 5 supporting conduction ofthe transistor or solid state switching device 38 can take place onlybetween the time when the core is switching from one saturated conditionof the one leg on which the winding 52 is wound until that portion ofthe core on which winding 33 is wound is saturated. As a result, thetime required to switch the saturable switching core 51 between the twopoints where a voltage is induced in the winding 75 is reduced as thecurrent through the winding 92 increases and this time is substantiallyinversely proportional to current through the winding 91.

The time that the transistor 36 is in its conducting state, therefore,is substantially inversely proportional to the magnitude of the currentthrough the winding 91 and hence is inversely proportional to theterminal voltage of the battery 27. It can be appreciated also that theamount of electrical energy stored in the electrical storage devicerepresented by the primary winding 11 of the ignition coil isproportional to both the terminal voltage of the battery 27 and the timethat the storage device or primary winding 11 of the ignition coil isenergized. As a result, the electrical energy stored in the electricalstorage device or primary winding 11 of ignition coil 10 will remainsubstantially constant independently of wide fluctuations in theterminal voltage of the battery 27, since as the terminal voltageincreases the amount of time that the electrical storage device orprimary winding 11 is energized prior to the requirement for ignitionvoltages in the secondary winding 12 varies substantially inversely tothe terminal voltage of the source of electrical energy or battery 27.

FIGURE 4 discloses a circuit diagram of another ignition system thatalso provides substantially constant output energy irrespective of andindependently wide fluctuations in the terminal voltage of the source ofelectrical energy or storage battery 27. It is similar to the circuitshown in FIGURE 1 with certain exceptions. It will be noted that thewinding 33 is connected in parallel with the primary winding 11 ratherthan being connected in series with the primary winding 11 as it is inthe circuit shown in FIGURE 1. Also, a zener diode 99 is connectedacross the winding 52 and the contact breaker points 58 and in serieswith the resistor 54. Hence, in effect a voltage divider circuitcomprising zener diode 99 and resistor 54 is connected across thebattery or source of electrical energy 27. It is poled in such adirection as to oppose the how of current in the voltage divider circuitcomprising the zener diode 99 and the resistor 54. Its breakdown value,however, is such that the lowest terminal voltage of the batteryexpected to be encountered is sufficient to break it down. As a result,it provides a constant voltage across its terminals. This zener diodemay be selected to provide a six volt drop across it which will remainsubstantially constant despite wide fluctuations in the terminal voltageof the source of electrical energy or battery 27. As a result, aconstant voltage is applied to the winding 52 when the ignition contactbreaker points 58 close.

In addition, a biasing winding 101 is positioned about the saturableswitching core or transformer 51. This winding has its dot markedterminal connected to the negative terminal 26 of the source ofelectrical energy 27 through lead 102, limiting resistor 103, lead 104,lead 31 and lead 28. The other end of the winding 101 is connected tothe positive terminal 44 of the battery 27 through lead 105, lead 42 andlead 43.

It can be readily appreciated that in the operation of this circuit, thewinding 101 is continuously coupled to the source of electrical energy27 thereby providing a bias on the core 51 that is opposite in directionto the bias provided by the winding 52 when the ignition contact breakerpoints 58 are closed. In other words, the flux produced by the winding101 is in the opposite direction to the fiux produced by the winding 52when the contact breaker points 58 are closed.

FIGURE 5 shows the hysteresis loop for the saturable switching core 51.The winding 52 produces a magnetomotive force having a negative value,as shown, and this in turn produces a flux tending to drive the coretoward a negative state of saturation. On the other hand, the winding101 produces 'a magnetomotive force in a positive direction that tendsto drive the core toward the positive state of saturation. The resultantflux in the core, therefore, when the ignition contact breaker points 58are closed, is the resultant flux produced by the net magnetomotiveforce resulting from the algebraic sum of the magnetomotive forcesproduced by the winding 52 and that produced by the winding 101.

It is apparent 'also that the magnetomotive force produced by thewinding 101 is directly proportional to the terminal voltage of thebattery or source of electrical energy 27. As a result, if the terminalvoltage of the source of electrical energy or battery 27 is six volts,the magnetomotive force in ampere turns produced by the winding 101 maybe that value designated by the letter D, while if the terminal voltageis twelve volts it may be the value designated by the letter E, and ifeighteen volts it may be the value designated by the letter F. Themagnetomotive force in ampere turns produced by the winding 52 when thecontact breaker points 58 are closed is a constant since the voltageacross the winding 52 is a constant determined by the zener diode 99.This value is designated by the letter G. Consequently, the resultingoperating point on the hysteresis loop is determined by the algebraicsum of these two values of magnetomotive force as stated above, and ifthe terminal voltage of the battery is six volts the operating pointwill be point A on the hysteresis loop, while if twelve points it willbe at point B, and if eighteen volts it will be at point C.

The magnetomotive forces produced by currents through the windings 101and 52 are selected so that the points A, B and C are located on thesubstantially straight line portion of the hysteresis loop and so thatthe distance from the saturated condition of the saturable switchingcore or transformer 51 at point H to the operating point is inverselyproportional to the current through the winding 101 and hence inverselyproportional to the terminal voltage of the battery 27. As shown, thedistance from the saturated condition at H to the operating point C isone-third of the distance from the point H to the point A, the distancefrom the saturated condition at H to the operating point B is two-thirdsthe distance from the saturated condition at H to the operating point A.As pointed out previously, the operating point A is determined by aterminal voltage of the battery 27 of six volts, the operating point Bis determined by a terminal voltage of the battery 27 of twelve volts,and the point C is determined by a terminal voltage of the battery 27 ofeighteen volts. Thus, as the terminal voltage increases in theseincremental amounts of six volts with the top voltage of eighteeenvolts, the distance between the saturated condition at H and theoperating point decreases proportionally in incremental amounts ofone-third. Thus, the time that a voltage is induced in the feedbackwinding 75 that turns the solid state switching device or transistor 36to its conducting state is inversely proportional to the terminalvoltage of the source of electrical energy or battery 27. As a result,the primary winding 11 will be energized for a period substantiallyinversely proportional to this terminal voltage.

It can be appreciated, therefore, that the ignition system shown inFIGURE 4 functions in precisely the same manner as the one shown inFIGURE 1 in which the transistor or solid state switching device 36 isswitched to its on state when the breaker points 58 are opened, and theperiod of this conducting state is determined by the time necessary toswitch the core from its operating point, for example, either A, B of C,to its saturated state at point H. Thus, the time that the solid stateswitching device or transistor 36 is in its conducting state and thetime the primary winding 11 of the ignition coil 10 is energized issubstantially inversely proportional to the terminal voltage of thesource of electrical energy or battery 27.

Since the electrical energy stored in the electrical storage device, theprimary winding 11 of ignition coil 10, is proportional to the terminalvoltage of the source of electrical energy or battery 27 and isinversely proportional to the time that it is energized from this sourceof electrical energy, the ignition system shown in FIG- URE 4 provides asubstantially constant amount of electrical energy to the electricalstorage device or primary winding 11 just prior to the requirement forignition voltages despite wide variations and fluctuations in theterminal voltage in the source of electrical energy 27.

It is readily apparent that this system may be used in a capacitivedischarge system as shown in my copending application S.N. 466,948,filed June 25, 1965, and that it is immaterial whether the energy isstored in an inductive core or transformer 51 from entering the crossbar 91 7 since the soft iron becomes in efiect a magnetic open circuitfor fast changing magnetic fields that appear in the core ortransformer. This construction still permits, however, the fiux in thebar 91 to vary as a function of the changes in the terminal voltage ofthe battery 27 since these changes are slow compared to the rapidlychanging fluxes in the saturable switching core or transformer 51.

In both of the embodiments of the invention shown in FIGURES 1 and 3,the time that the primary winding 11 of ignition coil 10 is energizedprior to the requirement for ignition voltages is independent of enginespeed. This is brought about by adjusting the parameters of thesaturable switching core or transformer 51 and the windings thereon suchthat the core 51 will always be switched to the saturated condition thatbrings about a generation of ignition voltages prior to the closing ofthe contact breaker points 58 that resets the core and commences anotherignition cycle.

The present invention thus provides an ignition systern in which theoutput energy supplied to the ignition devices or spark plugs of aninternal combustion engine is substantially constant irrespective of andindependently of wide fluctuations in the terminal voltage of the sourceof electrical energy supplying the ignition system. This is broughtabout by supplying an energy storage device in the system with aconstant amount of electrical energy irrespective of and independentlyof wide fluctuations in the terminal voltage of the source of electricalenergy just prior to the requirement for ignition voltages. As broughtout above, the output energy supplied to the ignition devices or sparkplugs is also independent of engine speed.

It is to be understood that this invention is not to be limited to theexact construction shown and described, but that various changes andmodifications may be made without departing from the spirit and scope ofthe invention as defined in the appended claims.

I claim: 7

1. An ignition system for an internal combustion engine comprising, asource of electrical energy, an ignition coil including a primarywinding and a secondary winding, a spark plug means operable insynchronism with the engine for coupling and decoupling said secondarywinding from and to said spark plug, and means coupling said primarywinding and said source of electrical energy for charging said primarywinding from said source of electrical energy to a substantiallyconstant value of electrical energy irrespective of wide fluctuations inthe terminal voltage of said source of electrical energy immediatelyprior to the requirement for ignition voltages in said secondary windingof said ignition coil, said means comprising a transistor, a saturableswitching transformer, circuit means coupling said transistor and saidsaturable switching transformer for causing said transistor to beswitched to a conducting state only during the time said saturableswitching transformer is switched from a steady state operatingcondition to one of its states of saturation, and circuit means coupledto said source of energy and said saturable switching transformer forbiasing said saturable switching transformer toward said one state ofsaturation as a function of the terminal voltage of said source ofelectrical energy.

2. The combination of claim 1 in which said last mentioned meanscomprises, a winding coupling said saturable switching transformer andconnected across said source of electrical energy.

3. An ignition system for an internal combustion engine comprising, asource of electrical energy, an ignition coil including a primarywinding and a secondary winding, a spark plug, means operable insynchronism with the engine for coupling and decoupling said secondarywinding from and to said spark plug, and means coupling said primarywinding and said source of electrical energy for charging said primarywinding from said source of electrical energy for a short time periodimmediately prior to the requirement for ignition voltages in saidsecondary winding of said ignition coil, said means comprising atransistor, a saturable switching transformer and circuit means couplingsaid transistor and said saturable switching transformer for causingsaid transistor to be switched to a conducting state only during thetime said saturable switching transformer is switched from a steadystate operating condition to one of its states of saturation, and meanscoupling said source of electrical energy and said saturable switchingtransformer for biasing said saturable switching transformer toward saidone state of saturation substantially proportional to the terminalvoltage of said source of electrical energy whereby said primary windingis energized with a substantially constant amount of electrical energyimmediately prior to the requirement for ignition voltages irrespectiveof engine speed and the terminal voltage of said source of electricalenergy.

4. An ignition system for an internal combustion engine comprising, asource of electrical energy, an ignition coil including a primarywinding and a secondary winding, a plurality of spark plugs, meansoperable in synchronism with the engine for sequentially coupling saidspark plugs to the secondary winding of said ignition coil, a solidstate switching device including an output circuit and an input circuit,a saturable switching core capable of being saturated in a first or asecond saturable state, a first winding coupled to said source ofelectrical energy and wound on said saturable core to bias saidsaturable switching core toward said first saturable state, a secondwinding coupling said source of electrical energy, said output circuitof said solid state switching device and said primary winding of saidignition coil and wound on said core in a direction to drive saidsaturable switching core into said second state of saturation, a thirdwinding wound on said saturable core and positioned in the input circuitof said solid state switching device, said third winding wound in apositive feedback direction with respect to said second winding, andmeans operable in synchronism with said first mentioned means forperiodically interrupting the coupling between said first winding andsaid source of electrical energy whereby said solid state switchingdevice is switched to its conducting state by the energy induced in saidthird winding and is maintained in its conductive state until saidsaturable switching core saturates in said second direction whereby saidprimary winding of said ignition coil is energized only during theperiod between the interruption of the coupling between said winding andsaid source of electrical energy and the saturation of said saturableswitching core in said second direction, and a fourth windingpermanently coupled to said source of electrical energy and wound onsaid saturable switching core in a direction to bias at least a portionof the saturable switching core toward said first state of saturation.

5. An ignition system for an interna combustion engine comprising, asource of electrical energy, an ignition coil including a primarywinding and a secondary winding, a plurality of spark plugs, meansoperable in synchronism with the internal combustion engine forsequentially coupling said spark plugs to said secondary winding of saidignition coil, a solid state switching device including an outputcircuit and an input circuit, said output circuit coupled to said sourceof electrical energy and said primary winding of said ignition coil forenergizing said primary winding from said source of electrical energywhen said solid state switching device is in a conducting state, asaturable switching core, circuit means coupling said source ofelectrical energy and said saturable switching core for biasing saidsaturable switching core toward one state of saturation, and decouplingmeans operable in synchronism with said first mentioned means fordecoupling said source of electrical energy and said saturable switchingcore, circuit means coupled to said saturable switching core, saidoutput and input circuit of said solid state switching device and saidsource of electrical energy for causing said saturable switching core tobe driven to the other state of saturation and for causing conduction ofsaid solid state switching device only during the period between thedecoupling of said source of electrical energy from said saturableswitching core and the saturation of said saturable switching core, andmeans coupling said source of electrical energy and said saturableswitching core and biasing said saturable switching core for shorteningsaid period substantially in proportion to the terminal voltage of saidbattery.

6. An ignition system for an internal combustion engine comprising, asource of electrical energy, an electrical storage means having an inputmeans and an output means, a spark plug, means operable in synchronismwith the engine for coupling and decoupling said output means of saidelectrical storage means from and to said spark plug, and means couplingsaid input means of said electrical storage means and said source ofelectrical energy for charging said electrical storage means from saidsource of electrical energy to a substantially constant value ofelectrical energy irrespective of wide fluctuations in the terminalvoltage of said source of electrical energy immediately prior to therequirements for ignition voltages from said electrical storage means,said means comprising a transistor, a saturable switching transformer,circuit means coupling said transistor and said saturable switchingtransformer for causing said transistor to be switched to a conductorstate only during the time said saturable switching transformer isswitched from a steady state operating condition to one of its states ofsaturation, and circuit means coupled to said source of energy and saidsaturable switching transformer for biasing said saturable switchingtransformer toward said one state of saturation as a function of theterminal voltage of said source of electrical energy.

7. The combination of claim 6 in which said last mentioned meanscomprises, a winding coupling said saturable switching transformer andconnected across said source of electrical energy.

8. An ignition system for an internal combustion engine comprising, asource of electrical energy, an electrical storage means having an inputmeans and an output means, a spark plug, means operable in synchronismwith the engine for coupling and decoupling said output means of saidelectrical storage means from and to said spark plug, and means couplingsaid input means of said electrical storage means and said source ofelectrical energy for charging said electrical storage means from saidsource of electrical energy for a short time period immediately prior tothe requirement for ignition voltages from electrical storage means,said means comprising a transistor, a saturable switching transformerand circuit means coupling said transistor and said saturable switchingtransformer for causing said transistor to be switched to a conductingstate only during the time said saturable switching transformer isswitched from a steady state operating condition to one of its states ofsaturation, and means coupling said source of electrical energy and saidsaturable switching transformer for biasing said saturable switchingtransformer toward said one state of saturation substantiallyproportional to the terminal voltage of said source of electrical energywhereby said electrical storage means is energized with a substantiallyconstant amount of electrical energy immediately prior to therequirement for ignition voltages irrespective of engine speed and theterminal voltage of said source of electrical energy.

9. An ignition system for an internal combustion engine comprising, asource of electrical energy, an electrical storage means including aninput means and an output means, a plurality of spark plugs, meansOperable in synchronism with the engine for sequentially coupling saidspark plugs to the output means of said electrical storage means, asolid state switching device including an output circuit and an inputcircuit, a saturable switching core capable of being saturated in afirst or a second saturable state, a first winding coupled to saidsource of electrical energy and wound on said saturable core to biassaid saturable switching core toward said first saturable state, asecond winding coupling said source of electrical energy, said outputcircuit of said solid state switching device and said input means ofsaid electrical storage means and wound on said core in a direction todrive said saturable switching core into said second state ofsaturation, a third winding wound on said saturable core and positionedin the input circuit of said solid state switching device, said thirdwinding wound in a positive feedback direction with respect to saidsecond winding, and means operable in synchronism with said firstmentioned means for periodically interrupting the coupling between saidfirst winding and said source of electrical energy whereby said solidstate switching device is switched to its conducting state by the energyinduced in said third winding and is maintained in its conductive stateuntil said saturable switching core saturates in said second directionwhereby said input means of said electrical storage means is energizedonly during the period between the interruption of the coupling betweensaid winding and said source of electrical energy and the saturation ofsaid saturable switching core in said second direction, and a fourthwinding permanently coupled to said source of electrical energy andwound on said saturable switching core in a direction to bias at least aportion of the saturable switching core toward said first state ofsaturation.

10. An ignition system for an internal combustion engine comprising, asource of electrical energy, an electrical storage means including aninput means and an output means, a plurality of spark plugs, meansoperable in synchronism with the internal combustion engine forsequentially coupling said spark plugs to said output means of saidelectrical storage means, a solid state switching device including anoutput circuit and an input circuit, said output circuit coupled to saidsource of electrical energy and said input means of said electricalstorage means for energizing said electrical storage means from saidsource of electrical energy when said solid state switching device is ina conducting state, a saturable switching core, circuit means couplingsaid source of electrical energy and said saturable switching core forbiasing said saturable switching core toward one state of saturation,and decoupling means operable in synchronism with said first mentionedmeans for decoupling said source of electrical energy and said saturableswitching core, circuit means coupled to said saturable switching core,said output and input circuit of said solid state switching device andsaid source of electrical energy for causing said saturable switchingcore to be driven to the other state of saturation and for causingconduction of said solid state switching device only during the periodbetween the decoupling of said source of electrical energy from saidsaturable switching core and the saturation of said saturable switchingcore, and means coupling said source of electrical energy and saidsaturable switching core and biasing said saturable switching core forshortening said period substantially in proportion to the terminalvoltage of said battery.

References Cited UNITED STATES PATENTS 3,169,212 2/ 1965 Walters 3152233,240,198 3/1966 Loudon et a1. 123148 3,306,275 2/ 1967 Hutton 123-1483,308,801 3/1967 Motto 123148 3,312,211 4/1967 Boyer 123-148 3,312,8604/1967 Sturm 315223 JAMES W. LAWRENCE, Primary Examiner.

C. R. CAMPBELL, Assistant Examiner.

